Incidence of rotary ProFile instrument fracture and the potential for bypassing in vivo

Aim To determine the incidence of rotary ProFile instrument fracture and the potential for bypassing in molar teeth in vivo. Methodology Four hundred and nineteen maxillary and mandibular first and second molars (1457 canals) were cleaned and shaped by two endodontists with new and used sets of nickel-titanium ProFile .04 taper rotary instruments. Each set of instruments was used in five molars and was steam-autoclaved before use. The canals were instrumented using passive instrumentation and a crown-down preparation technique. Instruments were examined both before and after use to evaluate whether breakage or deformation had occurred. All canals were instrumented to at least a size 30 at the working length. Results Nineteen instruments demonstrated visible signs of plastic deformation and were discarded and replaced, whilst 21 instruments underwent intracanal fracture during treatment. Amongst these, 14 fractured in the apical third, whilst the remaining seven fractured in the middle third. Seven instruments were bypassed, and treatment was completed. There was a significantly greater number of instrument fractures with the size 20 ProFile than with the other sizes, especially after the second time of use (P < 0.05). Conclusions Prolonged clinical use of ProFile nickel-titanium instruments increased their fracture rate. One-third of fractured instruments were bypassed.